Hydrofolding of metal



Nov. 15, 1960 D. P. RUTTER 2,960,141

HYDROFOLDING OF METAL Filed Deo. 26, 1957 INVIA/TOR 00A/ALD RRUTTL'R SYATTO/QN HYDROFOLDING F METAL Donald P. Rutter, Bernardsville, NJ.,assignor to Johns- Manville Corporation, New York, NSY., a corporationof New `fork Filed Dec. 26, 1957, Ser. No. 705,169

4 Claims. (Cl. 153-73) This invention relates to a method and apparatusfor producing grooves in thin metal sheets and is particularly directedto producing grooves in stainless steel or titanium metals.

In the hydro-forming processes for producing grooves in thin metalsheets the metal is stretched into the grooves. If this stretchingexceeds the elongation characteristics of the metal, serious structuraldefliciencies result. This is particularly true in the formation ofgenerally tubular insulating structures for airplanes where the innerskins must have deep circumferential grooves which can Withstandrelatively large collapsing forces. For other reasons, these structuresmust often be made of titanium, which has relatively little elongationcharacteristics. Thus, the usual hydro-forming methods for forminggrooves would result in serious structural deficiencies.

It is a primary object of this invention to provide a simple andeifective method and apparatus for forming grooves in metal, andparticularly in situations where substantial elongation of the metal inthe groove-forming operation is undesirable.

This invention provides apparatus for the hydro-folding of metal inwhich the grooves are essentially drawn into the metal. A die havinginternal ciriumferential grooves is adapted to receive a plug havingopenings adjacent to the grooves. A plurality of rubber sealing ringsare positioned in the plug to coincide with the lands between thegrooves in the die. Hydraulic fluid is forced through the openings toannular grooves in the plug between the sealing rings to force the metalinto the grooves. The grooves are formed in sequence working away from4the iirst groove toward the end of the metal so that there is nostretching of the metal. The axial length of the metal is shortened bythe drawing of the metal into the grooves. The resultant grooved metalhas no induced structural deficiencies in the grooved portions.

The invention will be more fully understood and further objects andadvantages thereof will become apparent when reference is made to thefollowing detailed description of a preferred embodiment of theinvention and the accompanying drawings in which:

Figs. l-4 are schematic representations in cross section of an apparatusfor the hydro-folding of metal; and

Fig. 5 is a rotated bottom plan view of the apparatus of Figs. l-4.

In Figs. 1 4, there is illustrated an apparatus for the hydro-folding ofgrooves in thin metal sheets. A cylindrical die 10, having a pluralityof grooves 11, 12 and 13 with corresponding lands 14 formed in the innersurface thereof, is adapted to receive the metal sheet 15 in which thegrooves are to be formed. The die is made in two sections which aredetachably secured together in any convenient manner. As illustrated inFig. 5, the die 10 is made in two semi-circular sections havinglongitudinal edge flanges 46. The sections are joined in operativerelation by nuts 47 and bolts 48 passing through openings in the anges.

A circular plug 16 tits within the die 10 so that the metal Sttes arentO sheet 15 may be received between the plug 16 and the die 10 and is sodesigned to provide for minimum tolerances between the die, the metaland the plug. The plug 16 has a plurality of circumferential, annulargrooves 17, 18, 19 and 20 which receive the rubber sealing rings 21, 22,23 and 24, respectively, so that each of the rings 21, 22, 23 and 24contacts the metal sheet 15 adjacent one of the lands 14. Under normalconditions the rings 21, 22, 23 and 24 allow the metal 15 to have arelative sliding movement to the plug 16 and the die 10. The grooves 17,18, 19 and 20 are connected respectively by passages 25, 26, 27 and 28to a source of hydraulic fluid, the pressu-re of which with regard tothe passages and grooves, is controlled respectively by two-positionvalves 29, 30, 31 and 32 which are connected to the passages 25, 26, 27and 28 by suitable fittings 53. This allows hydraulic fluid to be pumpedselectively into the grooves 17, 18, 19 and 20 to expand the sealingrings 21, 22, 23 and 24 to provide a positive seal and yet allow for therelative sliding movement of the metal 15 as desired. The valves 29, 30,31 and 32 are connected by the line 33 to a source of hydraulic fluid 34through a variable pressure pump 35. If it is desired, additionalpressure may be supplied to the grooves 17, 18, 19 and 20 to force therings 21, 22, 23 and 24 outwardly with sufficient pressure to preventthe relative sliding movement of the metal 15. This would be desiredwhere it was necessary to apply a small amount of stretching to themetal in the groove for setting purposes, as explained below.

The plug 16 is provided with a plurality of passages 36, 37 and 38leading respectively to circumferential, annular grooves 39, 40 and 41in the plug 16 located respectively between the sealing rings 21, 22, 23and 24. The hydraulic pressure in the passages 36, 37 and 38 iscontrolled respectively by two-position valves 42, 43 and 44 which areconnected by lines 45 and fittings 46 to the passages. The valves arecoupled to a supply line 47 in which hydraulic fluid is supplied from asource 48 by the variable pressure pump 49. Each valve 29, 30, 31, 32,42, 43 and 44 is provided with a drain pont 50 which is connected to acommon collection sump in any suitable manner. The hydraulic fluid underpressure, admitted in sequence between pairs of the sealing rings 21,22, 23 and 24, functions to force the metal 15 successively intoconformation with the grooves 11, 12 and 13.

The operation of the apparatus is illustrated in Figs. 1-4 whichdisclose the sequential formation of a plurality of grooves in a thinmetal sheet. As viewed in Fig. l, the metal sheet 15 has been positionedbetween the die 10 and the plug 16 so that the sheet 15 contacts thesealing rings 21, 22, 23 and 24. Hydraulic fluid under pressure frompump 35 is admitted by valves 29 and 30 through passages 25 yand 26 toextend the sealing rings 21 and 22 into sealing engagement with themetal 15. Hydraulic fluid under pressure from pump 49 is admittedthrough valve 42, passage 36 and annular groove 39 into the areaIbetween the sealing rings 21 and 22. The hydraulic fluid from pump 49,as illustrated in Fig. 2, forces the metal in the sheet 15 intoconformation with the groove 11. The sealing rings 21 and 22 prevent theescape of the hydraulic fluid but permit the metal to slide relative tothe sealing rings. As the lirst groove is formed, the transverse axiallength of the Imetal sheet 15 is'shortened as indicated by the dottedline 51.

Fig. 3 illustrates the formation of the second groove. The hydraulicpressure is maintained through the annular groove 39 on the metal in thegroove and also on seals 21 and 22. This forms a positive brake so thatthe pressure on the metal 15 in groove 11 prevents the axial movement ofthe metal 15. Valve 31 is opened allowing hydraulic fluid under pressurefrom pump 35 to flow through passage 27 to expand sealing ring 23 intosealing engagement with the metal 15. Valve 43 is opened to admithydraulic fluid under pressure through passage 37 and annular groove 40into the area between the sealing rings 22 and 23 to force the metal inthe tube into conformation with the groove 12. The sealing rings 22 and23 prevent the escape of hydraulic uid but the sealing ring 23 allowsthe metal sheet 15 to slide in an axial direction relative to lthe ring23. As the second groove is formed, the transverse axial length of themetal sheet 15 is further shortened as indicated by the increased lengthof the dotted line 51.

After the second groove has been formed, the hydraulic pressure in thearea of groove 11 is released by closing valve 42 which allows thehydraulic fluid to escape through port 50 to the collection sump. Valve32 is opened allowing hydraulic fluid under pressure from pump 35 toflow through passage 28 into groove 20 to expand the sealing ring 24outwardly into sealing engagement with the metal sheet 15. Valve 44 isopened to admit hydraulic fluid under pressure from pump 49 throughpassage 38 and annular groove 40 into the area between the sealing rings23 and 24 to force the metal in the sheet 15 into conformation with thegroove 13. The sealing rings 23 and 24 prevent the escape of thehydraulic fluid while the ring 24 allows for the relative transversesliding movement of the metal 15. As illustrated in Fig. 4, the axiallength of the tube 15 has been shortened the amount indicated by thedotted line 51 during the formation of the grooves. After the grooveshave been formed, the hydraulic pressure is released by closing all thevalves to allowthe hydraulic uid to empty through ports 55; the die isseparated, and the grooved metal sheet removed from the plug.

To satisfy specific requirements, it is sometimes necessary that therebe a slight stretching of the metal in the groove. The instant inventionhas incorporated therein apparatus for accomplishing the requiredstretching. If it is desired to impart a slight stretching, valves 29and 30 are opened to allow hydraulic fluid under pressure from pump 35to flow through passages 25 and 26 to expand sealing rings 23 and 24outwardly into sealing engagement with the metal sheet 15. Valve 42 isopened allowing hydraulic uid under pressure to ow through passage 36and groove 39 to force the metal in the sheet 15 between the sealingrings 21 and 22 outwardly. The hydraulic pressure acting through passage36 and groove 39 on the metal in the sheet 15 is regulated by the pump49 so that the metal is not forced completely into conformation with thegroove 11. The hydraulic pressure acting through passages 25 and 26 onthe sealing rings 21 and 22 is then increased by regulating the pump 35.This additional pressure on the sealing rings 21 and 22 forces thesealing rings 21 and 22 outwardly against the metal sheet 15 withsucient pressure to prevent the relative sliding movement of the metalon the sheet 15. The hydraulic pressure yacting through passage 36 andgroove 39 on the lmetal in the sheet 15 is then increased by regulatingthe pump fil-9 4so that the metal in the sheet 15 between the sealingrings 21 and 22 is stretched into conformation with the groove 11 in thedie 10. Thus, a predetermined amount of stretch may be imparted to themetal in the formation of the grooves. Succeeding grooves in the metalsheet 15 would be formed in sequence according to the steps illustratedabove.

Having thus described the invention in rather full detail, it will beunderstood that these details need not be strictly :adhered to and thatvarious changes and modifications may suggest themselves to one skilledin the art, all falling Within the scope of the invention asV defined bythe subjoined claims.

' What I claim is:

l. Apparatus for forming grooves in a thin metal sheet which is formedinto a generally tubular workpiece comprising a generally tubular diehaving a plurality of grooves formed in one sur-face thereof landadapted to receive the generally tubular work-piece to be grooved, acorresponding land between each of said grooves, a plug positionedwithin said die, said generally tubular work-piece being positionedbetween said die and said plug, a plurality of seals comprising arubberlike material on said plug and positioned to be in alignment withsaid lands and allowing for relative sliding movement between saidgenerally tubular work-piece and said seals, and means in said plug forsupplying hydraulic fluid under pressure to the area between adjacentpairs of said seals to sequentially force the metal in said generallytubular work-piece into conformation with said grooves.

2. Apparatus for forming grooves in a thin metal sheet which is formedinto a generally circular work-piece comprising a generally circular diehaving a plurality of circumferential grooves in the inner surfacethereof, said die being adapted to receive the generally circularworkpiece to be grooved, a corresponding land between adjacent grooves,a plug positioned within said die, said generally circular work-piecebeing positioned between said die and said plug, a plurality of sealingrings comprising a rubber-like material on said plug, said sealing ringsbeing positioned in alignment with said lands, said sealing ringscontacting said generally circular workpiece to form a plurality offluid tight compartments, each of said compartments being deined by saidplug, said generally circular work-piece and adjacent pairs of saidsealing rings, and means in said plug fo-r supplying hydraulic uid underpressure to said compartments in sequence to force the metal in saidgenerally circular Work-piece into conformation with said grooves sothat a plurality of grooves are successively formed in said generallycircular work-piece.

3. Apparatus for forming grooves in a thin metal sheet which is formedinto a generally circular work-piece comprising a generally circular diehaving a plurality of circumferential grooves formed in the innersurface thereof, said die being adapted to receive the generallycircular work-piece to be grooved, a corresponding land between adjacentgrooves, a plug positioned within said die, said generally circularwork-piece being positioned between said die and said plug, a pluralityof sealing rings comprising a rubber-like material on said plug, saidsealing rings contacting said generally circular workpiece to allow forrelative sliding movement between said generally circular work-piece andsaid sealing rings, said sealing rings being positioned in alignmentwith said lands, said sealing rings contacting said generally circularwork-piece to form a plurality of uid tight compartments, each of saidcompartments being defined by said plug, said generally circularwork-piece and adjacent pairs of said sealing rings, and means in saidplug for supplying hydraulic fluid under pressure to each of saidcompartments in sequence to force the metal in said generally circularwork-piece into conformation with the grooves in said die.

4. Apparatus for forming grooves in -a thin metal sheet which is formedinto a generally circular Workpiece comprising a generally circular diehaving a plurality of circumferential grooves formed in the innersurface thereof, said die being adapted to receive the generallycircular work-piece to be grooved, a plurality of corresponding landsbetween adjacent grooves, a hollow generally circular plug adapted to bepositioned within said die, said generally circular work-piece beingpositioned between said die and said plug, a plurality of sealing ringscomprising a rubber-like material seated in annular grooves in saidplug, said sealing rings positioned to be in alignment with said lands,said sealing rings contacting said generally circular work-piece to forma plurality of fluid tight compartments, each of said compartments beingdefined by said plug, said generally circular work-piece and adjacentpairs of said sealing rings,

said sealing rings allowing for relative sliding movement between saidrings and said generally circular work-piece, means in said plug forsupplying hydraulic uid under pressure to each of said compartments insequence to force the metal in said generally circular work-piece intopartial conformation with an aligned groove in said die, means forsupplying hydraulic fluid under pressure to expand a predetermined pairof sealing rings outwardly to prevent relative sliding movement betweensaid rings and said generally circular work-piece, and means to increasethe pressure in said compartment to stretch the metal in said generallycircular work-piece between said pair tof sealing rings into completeconformation with the aligned groove in said die.

References Cited in the le of this patent UNITED STATES PATENTS2,372,917 Tuttle Apr. 3, 1945 2,458,854 Hull et al. Ian. l1, 19492,460,580 Huber Feb. 1, 1949 2,479,702 Rood Aug. 23, 1949 FOREIGNPATENTS 1,136,143 France Dec. 22, 1956 UNITED STATES PATENT oEEICECERTIFICATE CORRECTION Patent No. 2,960, 141- November` 15, 1960 yDonald B. Rutter :It s hereby certified that error appears in the abovenumbered patent requiring correction and that the said Letters Patentshould read as corrected below.

Column 2, line 53, for "extend" read expand Signed and sealed this 21stday of November 1961.

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer DAVIDL. LADD Commissioner of PatentsUSCOMM-DC

